Lisa did an excellent in-depth review of the Treo 650 after she played with all version of the device (Cingular, Sprint and unlocked). The review includes pictures of all three versions and other great info. Read the review here:

How can I tell if my treo 650 is gsm or not? it is the palm one alltel treo 650. I just bought if from eBay, and like a real dummy, I didn't ask those two important questions..."is it gsm, and does it take a sim card?"

Now that I have had the 650 for nearly 4 yrs or so, what is the next step in treos or PDAs the delivery the ablility to do what it does. No one is talking about what to go to when it is time to upgrade?????!!!!!

If you are buying a used Treo 650, watch out for the earpiece and speaker phone. Many have stopped working, and repairs are expensive. Look out for whether it's a GSM (uses a SIM card) or CDMA version. You MUST have the correct one depending on YOUR cell service provider. Of course, that's true of all Cell Phones!